Mechanical artifical hand



April 17, 1951 J. H. SIMPSON MECHANICAL ARTIFICIAL H AND z Sheets-Sheet 2 Filed Jan. 20, 1947 lnvenlol J52? fi zlmpfon A llorlzeys Patented Apr. 17, 1951 MECHANICAL ARTIFICIAL HAND John Harold Simpson, County Down, Northern Ireland Application January 20, 1947, Serial No. 723,113 In Great Britain January 31, 1946 6 Claims. 1

[This invention relates to artificial hands and more particularly to such hands for use by a wearer who only has the stump of the arm remaining above or below the elbow.

Such artificial hands are known in which the fingers are articulated and pivotally mounted on a palm part in turn mounted on a sheath, bucket or the like for attachment to the wearers stump. A compensating linkage is mounted in the palm part and connected to the articulated fingers while a ratchet device mounted on the palm part or sheath, bucket or the like is provided and operatively connected to the ratchet mechanism, the arrangement being such that the wearer by moving another part or parts of his body operates the ratchet device through the harness and thus actuates the compensating linkage to open or close the artificial hand or cause the fingers to grasp objects while by another move mentof the wearers body the closed or gripping fingers are opened or the ratchet device is re-' leased so that the fingers open freely and rapidly under the action of a spring or other means.

having the minimum of working parts and which will be easy to operate and 'will resemble a natural hand in appearance and operation.

' Operating means according to the present invention are provided whereby when the fingers are stopped from moving forward by the object to be gripped but, at the same time, the pawl is not firmly engaged by a tooth of the rack. further relative movement of the rack with respect to the compensating linkage against an increasing force is provided, thereby to allow the pawl to engage the next tooth of the rack and to increase the grip exerted by the fingers.

The said operating means is preferably contained within the hand, and controlled by harness secured to the wearers body and connected to the artificial hand by flexible movementtransmitting mechanism such as a Bowden cable; the arrangement is such that movement of the wearers shoulder or other part of body operates the artificial hand. The shoulder operating mechanism and the belt are preferably interconnected andboth adapted to operate one or 2 more flexible transmitting mechanisms suchas Bowden cables to operate the hand.

To enable the invention to be more fully understood it will now be described with reference to the accompanying drawings in which: I

Fig. 1 is a view showing a right hand of a construction according to the invention, with the thumb omitted;

Fig. 2 is a longitudinal cross-section through the forefinger of the right hand shown inFig. 1 indicating in dotted lines the position of the forefinger when the hand is closed;

Fig. 3 is a view of a form of harness adapted for use with a left hand similar to the right hand shown in Figs. 1 and 2 as applied to a wearer having no natural left hand, and seen from the wearers front; I

Fig. 4 is a front view of a detail shown in Figs. 1 and 2, drawn to a larger scale; and

Fig. 5 is a side elevation of Fig. 4 looking from the right in that figure.

Referring to Figs. 1-5 the artificial hand shown therein is formed to approximately the shape of a natural hand with four independent fingers 1-4 and a thumb (not shown). Each finger is pivoted at its root 1 to the palm part 6 and is provided with a joint 8 in the central portion thereof; the top or outer finger joint is omitted and the tips may be straight or crooked to any desired angle.

The finger root joints are all formed by a common pivot pin 209 and the central joints 8 are formed by separate pivot pins 209a. .The finger roots are formed with a central slotted portion 2H] and are cut away at 2H to fit into slots 2| 2 in the palm part 6. The cut-away portions 2 are bored to form a journal for thepin 209 and the finger roots and palm part are shaped'so as to allow the fingers to rotate about the palm part to close the fingers in a gripping action.

The joints 8 are formed in a similar way to j the joints 1 except that there is a separate .pin 209a. for each finger.

A guide 2|3 is secured to the palm part6, in which a slide 2! is adapted to reciprocate. One side of the slide 2 I4 is provided with a series of ratchet teeth 2l5 and a spring urged pawl 2I6 pivotally mounted on the guide 2l3, is adapted to engage the teeth and hold the slide 2M in one of several positions. The pawl H6 is urged into contact with the ratchet teeth by a spring 2|? fixed on the guide 2l3. The pawl 2l6 carries a pin 2l 8 which extends above the guide and engages a slot in a bellcrank lever 219 pivotally mounted on the guide at 220. Thus by moving the lever 219 the pawl 216 is moved out of engagement with the teeth 215 against the action of the spring 211.

The lower finger portions are operatively connected to floating members 223 by rods 221 which are pivotally attached to the finger portions at 222 and to the members 223 by links 224, the latter forming universal joints. The members 223 are pivotally mounted on a yoke 225 in turn rotatably mounted on a pin 225 secured to the slide 214. A tension spring 227 is connected at one end to the yoke 225 and at the other end to the palm part 6 near the finger roots. An arbor 228 fixed to the guide 213 has a drum 223 rotatably mounted thereon. .lA-fine .chaimcable, wire or the like 230 is secured at one. end to the drum 229 and at its other end to the yoke 225, the drum being slotted or grooved at 231 so that on rotation (in Fig. l, clockwise) the chain 233 is wound thereon. A radial lever 232 is secured to the drum.

The outer parts of the fingers (above joint 1) are connected by rods 233 to rods 234. The rods 233 are pivoted to the finger parts at 237 and to the rods 234 at 25 I. The rods" 234 are mounted on the pin 239 and held against movement by pin 235 fixed in the palm part and passing through the rods 234. The rods 221 and 233 pass through the slotted portions 210 and 236 respectively of the finger parts. The pivots 232 and 231 are arranged eccentrically of the pivot pins 209 and 239a.

Flexible transmission-members 238 and 239 are connected to the'extremities 2413 and 241 of the I levers 232 and 219 respectively, and are provided with hooks or the like (not shown) at their free ends.

The yoke 225 is-bored at 2 12 (Figs, 4 and 5) to receive the arbor 226, the boring being elongated at 243. A rubber or like resilient block 24 5 is inserted in the boring at one side of the arbor 226. The block 244 is curved to fit the gap between the circular arbor and the extremity of the elongated boring. A metal or like plate 245 having a curved face to engage the arbor and a fiat 'face in contact with the rubber block may be interposed as in Fig. 5 to reduce the wear of the rubber block.

Referring to Fig. 3 the harness comprises a 1 flexion thong 53 ending in the sheath 15 with a hook 243and is adapted to be connected under tension to' the flexible transmission-member 239: also the casing of the Bowden cable 47 or like flexible transmission member is anchored at 231 to the link 44 and the inner cable248 is extended and connectedto the D-shaped member 243 on the shoulder loop 41. Ihe other end of the Bowden cable casing is anchored to the sheath 15 and the inner cable ends in a hook or the like 250 adapted to beconnected withoutany slack to the free end of the flexible.transmitting-member 238.

To operate the hand, the wearer raises the right shoulder thereby pulling the cable 238 and through the flexible transmission member 238 rotates lever 232 to pull chain 230 and yoke 225 wristwards against the action of the spring 221. The pawl 216 rides over the teeth 2i5, but by successively re-engaging each tooth under the action of spring 2H, holds the slide against the returning action of spring 221. Wristward movement of yoke 225 and with it' the floating members 223, pulls the rods 221 which being eccentrically mounted on the fingers at 222 causes the 4. lower parts of the fingers to rotate in hand-closing direction. Because of the eccentric mounting of the rods 233 the upper finger portions as they move with the lower finger portions, also rotate about said lower finger portions to simulate the complete closing or clenching movement of a natural hand.

When it. is desired to re-open the closed or semi-closed artificial hand, flexing of the wear-v ers body will cause the fiexion thong 50 to pull 'the flexible transmitting-member 239 and thereby move the lever 219 to disengage the pawl 215 from teeth 215 so that the yoke 225 moves away from the wrist under the action of spring 221 to open the hand again.

If during the. closing movement one or more of the fingers 14 engages an object, further pull on the member 238 will increase the grip on such object while the remaining fingers continue closing since yoke 225 will rotate on arbor 223 and the members 223 iwillrotate aboutthe yoke 225 and -rods.22.1.

If the hand has been fully closed with or without gripping an object, the grip may not be strong because pawl 216 having traversed only part of the succeeding ratchet tooth will not trip over said tooth and moves back to the preceding tooth. An extra raising'of the wearers right shoulder will then cause the arbor to compress the block 243 since yoke'225 cannot move further, thereby causing teeth 215 to move asmall distance past the'pawl 216 and allow the pawl to engage the succeeding tooth and efiect an added grip of the fingers.

While movement of the lever 2.19 to releasethe pawl 216 has been described as being effected by action of the fiexion thong, it may be efiected through suitable addition to the harness, by movement of other parts of the wearers body, with or without the employment of a fiexion thong.

The length of the levers 232 and 219 may be varied as desired; or the levers may be replaced by any suitable mechanism. The spring 221 may be arranged to operate in compression and may consist of a spring steel helical spring, or any other form of spring; or a rubber or other resilient member may be employed.

The adjustable wrist means 11-23 and thumb means 2534 are adapted normally to be operated by the wearers other hand.

The artificial hand may be made up ofv a suitable combination of light metal parts and plastics or other suitable materials for example, acrylic resins or polyvinyl chloride and the palm or other parts, such as the finger tips may have suitable rubber or flexible plasticor like pads.

I claim:

1. An artificial hand'comprising a palm, fi.ngers articulatedon said palm, a guide secured to said palm and having a spring pressed pawl, a slidev confined Within said'guide, a ratchet. on said .slide,..finger. actuating means-between said slide and said fingers, resilient means between said finger actuatingv means. and said slide,..and slide actuating means secured to said palm whereby when the fingers are stopped from moving. forward by an object to be gripped further relative movement of said ratchet with respect to said pawl against the increasing force is provided to allow the pawl to seat behind the next tooth of said ratchet and thereby to increase the grip exerted by said fingers.

2. A mechanical artificial'hand comprising'a palm part, a finger root joint comprising a' common pivot pin, fingers pivotally attached to said palm part by said pivot pin forming an axis of pivot for said fingersfa guide carried by said palm part having a channel way therein coplanar with the axis of pivot of said fingers, a slide reciprocatingly carried in said channel, retaining means forholding said slide in said guide, link means for joining pairs of adjacent fingers, an equalizer block for said link means secured to and movable with said slide for simultaneously opening and closing all of said fingers, spring means for normally biasing said equalizer block and fingers to the fully extended position, means for drawing said fingers to a closed position, and latch release means for releasing said fingers from a closed position, to the fully extended or I means is a bellcrank arm pivoted on said guide 30 with the shorter arm positioned to contact and 6 disengage the retaining means and the longer arm adapter to be actuated for pivoting said bellcrank arm and releasing the ratchet mechanism and allowing the fingers to extend to their fully extended position.

6. An artificial hand as claimed in claim 2 wherein said means for drawing the fingers to the closed position is a drum rotatably carried by said guide having a chain one end of which is connected thereto and the other end of which is connected to the equalizer block, said drum being actuated by a pivoted lever.

JOHN HAROLD SIMPSON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 999,484 Carnes Aug. 1, 1911 1,466,163 Harris Aug. 28, 1923 1,484,913 Surry Feb. 26, 1924 1,569,286 Laherty Jan. 12, 1926 2,364,313 Pecorella Dec.'5, 1944 2,464,577 Hobbs Mar. 15, 1949 FOREIGN PATENTS Number Country Date 127,599 Great Britain Nov. '27, 1919 301,803 Germany Nov. 5, 1917 

